#include "stdio.h"

int main()
{
	float temp = 0.0, sum = 0.0;
	for(int i = 0; i < 12; i++)
	{
		scanf("%f", &temp);
		sum += temp;
	}
	float average = sum / (float)12;
	printf("$%.2f", average);
	return 0;
}